Drop-out fuse



at w W 7/ 7///// 7///////////////// l /M w I I 51 a 7/////////4y//A ZTEefo H HH l) L Patented Oct. 8, 1940 UNITED STATES- PATENT OFFICE 8 Claims.

This invention relates to drop-out fuses for high tension transmission lines and aims to provide important improvements on fuses of the general type shown in my Patent No. 2,074,913,

the main idea being to provide novel guide and ejector means for the fuse lead or at the lower end of the fuse tube to prevent kinking of the leadagainst the end of the tube which might lock the mechanism and cause the tube to remain in place after the fuse blows. Further, the idea is to provide cam guide means for the lead to hold it out of contact with the inside wall of the tube and thereby prevent charring the tube when the lead is heated due to an overload. Also, the invention provides a lead guide which exerts a cam action on the lead when the fuse blows to drag the separated portion quickly down the tube and permit the hinge or toggle mechanism to operate freely and almost instantaneously through the to entire stroke.

Other aims and advantages of the invention will appear in the specification, when considered in connection with the accompanying drawing,

wherein:

25 Fig, 1 is a side elevation of a fuse assembly embodying the invention;

Fig. 2 is an enlarged vertical sectional view of the fuse unit in Fig. 1;

Fig. 3 is a fragmentary sectional view showing 80 the position of the parts immediately after the fuse blows; and

Fig. 4 is a bottom plan view of the fuse unit.

Referring particularly to the drawing, the preferred embodiment of the invention is applied to a $5 drop-out fuse of the type shown and claimed in my Patent No. 2,074,913, it being understood that it is applicable to many other types of drop-out fuse units, either single or multiple.

Herein the drop-out fuse assembly is shown as 0 being applied to a cross arm ill of an ordinary pole type transmission line, although it is to be understood that it may be mounted on any supporting structure. In this instance, it is supported by a strap metal bracket Ii depending 45 from the cross arm and having a clamping plate 12 for securing it on one side of the cross arm by means of bolts l3. The bracket Ii is slightly resilient and is here shown as being bolted at its lower end to a clamp H on a. single bushing type 50 insulator i5. This clamp is preferably secured in the middle of the insulator and the insulator is supported at an acute angle to the vertical, the bracket Ii being suitably bent for that purpose. The insulator is shown as having spring arms i8 85 and il extending outwardly and laterally from the upper and lower ends. Also, terminal lugs ill and I! are bolted against the inner ends of the arms and have line clamps and 2| respectively.

In the present example, the fuse holder is carried by the outer ends of the spring arms i6 and i1 and is arranged to drop out initially and then swing downwardly. For this purpose, the lower bracket is shown as having a pair of spaced hinge elements or ears 22 secured thereto preferably by rivets, as shown in Fig. 1, each ear having a 10 trunnion guiding slot 23 and an offset trunnion bearing 24 at the bottom. The switch fuse unit is shown as consisting of an ordinary insulating fuse tube 25, preferably made of Bakelite, and having a clamping collar 26 secured near its lower 15 end. The clamping collar 26 has trunnions 21 pivotally connected to arms 28 on a hinge or toggle element 29 so shaped at its lower end as to embrace or straddle the lower portion of the fuse tube and also presenting trunnions 30 joumaled go in the bearings 24. The fuse tube carries a fuse link 3| and an ordinary removable fuse lead 32, the free end of which is adapted to be secured under slight tension by a clamping bolt 33 on the rear of the toggle member 29. Also, the toggle member carries an upwardly extending hook eye 34 adapted to limit the swinging movement of the tube in the toggle member. The upper end of the fuse tube carries an ordinary metal ferrule 35 having a hook eye 38 on its front portion adapted to be engaged by an ordinary switch hook to swing the fuse unit to its closed position. The upper end of the ferrule is closed by a removable screw cap 31 adapted to engage the upper terminal of the fuse element. This cap is shown as having a dome shaped upper end 38 cooperating with a cast metal terminal member 39 riveted to the outer end of the upper spring arm it.

All of the mechanism thus far described is substantially the same as that shown in my afore- 40 said patent. However, the fuse lead shown in the said patent is bent around the lower end edge of the tube. This is objectionable if large leads are employed because the sharply bent portion does not readily straighten and therefore locks the mechanism which prevents the tube from dropping out. Moreover, small leads when bent around the lower end of the tubes will stretch and sometimes char or burn the tube when they are in contact with it due to heating caused by overloads.

In accordance with this invention, the lower rear portion of the toggle carries a cam shaped guide element 40 shown as being pivoted on a lug 4| and having a groove 42 to accommodate the lead. The cam has a free end 43 projecting up wardly into the lower open end of the tube and an inner smooth cam face 44 engaging the inside edge of the tube at the lower end. As explained in the aforesaid patent, the fuse tube is biased to swing toward its drop-out position primarily by the compression of the spring arms i8 and il acting on the compound toggle hinges. The stiff leg position is further adapted to be initially broken by a spring contact plunger 4! acting against a contact face 46 on the rear of the toggle member.

Now, the shape of the cam member 4| is such that the tube, when it is initially swung outwardly and downwardly, will turn or swing the cam outwardly on its pivot (Fig. 3) and cause it to drag out the lead, eliminating friction between the lead and the tube. Also, it acts instantaneously and permits the compound hinges and toggle mechanism to operate freely. Further, it holds. the fuse lead practically centrally in and out of contact with the tube to prevent charring of the inside of the tube. It transmits the lead tension directly to the toggle member. The ejec- :or action caused by the initial drop-out movement of the tube cooperating with the cam quickly parts the blown fuse and thereby reduces arcing. In fact, cam guides and ejectors of this type have proved to be eminently satisfactory in commercial fuses and are almost indispensable in drop-out units having large and relatively stiif leads. Also, they insure quick and positive drop-out action throughout the stroke of the mechanism. I

Obviously, the present invention is not restricted to the particular embodiment thereof herein shown and described. Moreover, it is not indispensable that all the features of the inven-- tion be used conjointly, since they may be employed advantageously in various combinations and sub-combinations.

What is claimed is:

1. In a drop-out fuse of the class described, a fuse tube having an open lower end; a tensioned fuse lead projecting through the open end of the tube and bent upwardly; a toggle member to which the end of the fuse lead is secured; and a guide element on the toggle member normally extending iuto'the open end of the tube over which the lead is trained to hold it out of contact with the tube.

2. In a drop-out fuse of the class described, a fuse tube having an open lower end; a tensioned fuse lead projecting through the open end of the tube and bent upwardly; a toggle member to which the end of the fuse lead is secured; and a cam-shaped guide element on the toggle member normally extending into the open end of the tube over which the lead is trained to hold it out of contact with the tube.

3. In a drop-out fuse of the class described, a fuse tube having an open lower end; a tensioned fuse lead projecting through the open end of the tube and bent upwardly; a hinge member pivotally secured to the lower end portion of the tube having clamping means to secure the end of the fuse lead; and a pivoted guide element for the fuse lead mounted on the lower end of the hinge member and projecting into the open end of the tube.

4. In a drop-out fuse of the class described. a fuse tube having an open lower end 1 a tensioned fuse lead projecting through the open end of the tube and bent upwardly; a toggle member to which the end of the fuse lead is secured; and a cam shaped guide element for the fuse lead pivotally connected to the toggle member and having a groove for holding the lead spaced from the wall of the tube.

5. In a drop-out fuse of the class described, a fuse tube having an open lower end; a tensioned fuse lead projecting through the open end of the tube and bent upwardly; a toggle member to which the end of the fuse lead is secured; and a cam shaped guide element for the fuse lead pivoted on the toggle member and having its free end projecting into the open end of the tube.

6. In a drop-out fuse of the class described, a fuse tube having an open lower end; a tensioned fuse lead projecting through the open end of the tube and bent upwardly; a toggle member to which the end of the fuse lead is secured; a grooved, cam shaped guide element for the fuse lead pivoted to the back of the toggle member and projecting into the open end of the tube; and a rear cam face on said guide element coacting with the lower end of the tube to cause the element to swing on its pivot due to the initial dropout movement of the tube and thereby drag the lead outwardly.

7. In a drop-out fuse of the class described, a fuse tube having an open lower end; a tensioned fuse lead projecting through the open end of the tube and bent upwardly; a trunnioned member having arms on which the fuse tube is pivotally mounted above its lower end; a curved grooved guide member for the fuse lead carried by the trunnioned member extending into the lower end of the tube to hold the lead out of kinking and burning contact with the lower end of the tube.

8. In a drop-out fuse assembly of the class described having a pivotally mounted fuse tube open at its lower end; a toggle member supporting the tube for drop-out movement; a fuse lead projecting through the open end of the tube; clamping means for the end of the fuse lead on the toggle member; a grooved cam shaped guide element for the lead pivoted to the toggle member near the lower end of the tube and projecting into the open end of the tube; spring means biasing the tube to swing outwardly; and a cam face on the guide element adapted to be engaged by the tube to swing the guide element outwardly from the tube and drag the fuse lead with it due to the initial drop-out movement of the tube when the fuse blows.

TOMLINSON F. JOHNSON. 

